It is common practice in highway-railroad grade crossing warning systems for control circuitry to consist of an arrangement of electromagnetic relays operating on 12 volts DC, or electronic processor equivalent inputs and outputs (I/O) operating on the same voltage. The control circuitry, which controls flashing of the lights and, when used, operates the gates, receives its input from train detection circuit outputs. The control and train detection circuitry operate on closed circuit fail-safe design principles. An electrical interruption, such as a short circuit or open circuit in the circuitry, results in activation of the warning devices. That is, the flashing lights are activated and the gates, when used, are caused to descend.
During routine signal or track maintenance activities that activate the warning devices, or when a malfunction occurs in the train detection circuitry that activates the warning devices, maintenance personnel can simulate repair or turn off the devices by connecting an electrical jumper between an appropriate voltage source and the malfunctioning control input. The result is a deactivation of the warning devices which turns the flashing lights off and which returns the gate arms to the vertical position. This situation is referred to as an “Out of Service” mode because a train will not be detected on the affected track or tracks. Since the input to the system is falsely energized in a manner that is electrically the same as normal operation, the system cannot differentiate the false energization from the normal operation.
The industry recognizes that the placement of a jumper in the circuitry to cause one or more tracks to be placed out of service is subject to human error. At least one fatal accident has occurred due to failure to remove a jumper after completion of maintenance work. After maintenance work has been completed, the signal maintainer needs to remove the jumper wire from the grade crossing control relay and verify the operational status of the grade crossing equipment as required by established railroad procedures.
A general object of the present invention is to provide a highway-rail grade crossing controller with an improved out of service capability.
Another object of the present invention is to provide a highway-rail grade crossing controller with an out of service capability for an approach circuit, an island circuit, or both.
A further object of the present invention is to provide a highway-rail grade crossing controller with such an out of service capability that requires confirmation that the maintainer wants to take a track out of service to minimize human error.
Yet another object of the present invention is to provide a highway-rail grade crossing controller with such an out of service capability with a timer that will return an out of service track to normal operation upon expiration of selected time interval.
A still further object of the present invention is to provide a highway-rail grade crossing controller that notifies a railroad operations control center of an out of service mode, and that further notifies the railroad operations control center when the crossing is returned to service.